Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

"We know that relationships change the way we think about ourselves," lead author Erica Slotter, a psychology Ph.D. candidate at Northwestern University in Illinois, told LiveScience. "When a relationship ends, that sense of self ends."

Couples often share friends, do the same things in their free time, and talk about the future. They say things like, "We like traveling," and finish each other’s sentences. The more committed they are to one another, the harder it is for them to distinguish their individual differences, the researchers describe in the February issue of the journal Personality and Social Psychology Bulletin.

"There's some overlap between my self and my partner's self, they say," Slotter explained. When the couple breaks up, "all those pieces that they shared are not meaningful anymore, because the relationship is defunct."

And not having a clear idea of who you are without your partner can lead to emotional distress, the authors write.

You Complete MeThe researchers conducted three studies to figure out how their undergraduate volunteers thought of themselves during and after their relationships.

In the first, one group of Northwestern students answered questionnaires asking whether they changed their appearance, activities, social circle, future plans, or values after going through a breakup. The results showed that the participants experienced a moderate, but significant change in their perception of themselves, saying that their values or beliefs changed, or that they altered their appearances after their last relationship ended.

Another set of students who indicated they were in a relationship answered questions about how they imagined they might change if the romance ended. Results showed the more committed a participant was to the relationship, the more that person thought he or she would change after a breakup.
Video: Finding love on Facebook

In the second study, Slotter and her colleagues looked at diary entries, or blogs, that referenced life-changing events like a breakup or a career change. They found that of 76 diaries, people who wrote about a breakup had a hazier idea of who they were, using words like "confuse," "uncertain," and "bewilder" more often than those who wrote about other experiences. The findings suggested individuals who had gone through romantic breakups had a more muddled self perception.

Healing the WholeTo find out more about how breakups and the loss of a clear sense of self affected emotional well-being, the research team had 69 college freshmen participate in a six-month study. Participants were interviewed and asked filled out questionnaires every other week. During that timeframe, more than a third of the participants' relationships ended. Those students who had split up with partners were more emotionally distressed at the end of the study, the analysis shows.

"Romantic relationships can provide some of the richest emotional rewards of adulthood, but they can also leave us achingly vulnerable," the researchers write. Uncovering that individuals change the way they think about themselves when entwined in a romantic relationship, how that changes when they break up, and the resulting emotional stress, could help individuals keep their chins up post breakup.

"From a research standpoint, it's a totally new piece of the puzzle," said Slotter, who plans to expand upon her work. "The research that we're doing right now is looking into how the self might be repaired after a relationship ends," she said.